Tasmanian devils’ survival at risk

By CARL ZIMMER The New York TimesPublished January 26, 2013 - 5:16am Last Updated January 26, 2013 - 9:59am

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Cancer epidemic threatens species

A young Tasmanian devil, which is free of disease, emerges from a tube on its new home on Maria Island. (NEW YORK TIMES)

In November, a team of biologists journeyed to Maria Island, three miles off the Australian island state of Tasmania, taking with them 15 plastic cylinders. They loaded the cylinders into SUVs, drove them to an abandoned farm and scattered them in the fields.

Before long 15 Tasmanian devils emerged from the containers, becoming the first ever to inhabit the island.

“All indications are that they’re doing very well,” Phil Wise, a government wildlife biologist who leads the project, said of the devils — fierce-looking, doglike marsupials that have become an endangered species on the much larger island for which they are named.

This spring the team plans to take more devils to Maria. The goal is to establish a healthy colony that will endure for decades to come. The stakes of the project are high: the survival of the entire species may depend on it.

Many species are threatened with extinction, but the Tasmanian devil faces a singular enemy: an epidemic of cancer. A type of facial tumor has in effect evolved into a parasite, with the ability to spread quickly from one devil to another, killing its victims in a few months.

“We have very little time to save the species,” said Katherine Belov, a biologist at the University of Sydney.

An international network of biologists has spent the past decade figuring out this new kind of disease.

“It’s been quite a struggle just to learn some of the basics,” said Elizabeth Murchison, of the University of Cambridge in England.

But recently Murchison and other experts have gained important insights into how the cancer evolved into a parasite. Some scientists are now trying to translate that knowledge into a treatment, perhaps a cancer vaccine.

There is no guarantee that these projects will save the devils, so Wise and his colleagues are setting up a drastic Plan B: They are establishing Maria Island as a cancer-free refuge for wild Tasmanian devils.

Then, if the devils die out in Tasmania, Belov said, “the disease will be gone from the mainland, and then they can be introduced back in the wild.”

Biologists first encountered the cancer in the late 1990s. The tumors grew on the devils’ faces or inside their mouths, and within six months the animals were dead. The first cases appeared in eastern Tasmania, and with each passing year the cancer’s range expanded westward.

When scientists examined the cells in the tumors, they got a baffling surprise. The DNA from each tumor did not match the Tasmanian devil on which it grew. Instead, it matched the tumors on other devils. That meant that the cancer was contagious, spreading from one animal to another.

Until recently, most scientists believed Tasmanian devils were uniquely vulnerable to contagious cancers. They have very little genetic diversity, and so they might not be able to recognize a tumor as foreign.

In case no medicine works, the federal and Tasmanian governments are quarantining a so-called “insurance population” of devils. The program now has 500 cancer-free Tasmanian devils in zoos and sanctuaries. It is to ensure they do not become too tame to survive on their own that Wise and his colleagues are establishing the wild population on Maria Island.